fix(minecraft): update 26.3 server artifacts

[druid-infra]

Summary

• Fix the Minecraft Vanilla 26.3 server download to the live Mojang server artifact.
• Fix the PaperMC 26.3 installer to request the 26.3 snapshot-cache artifact.

Verification

• Mojang version metadata reports release 26.3 and server SHA-1 33680f5f2ac32864d6d7cf5e56a705fdb3e05f4c.
• Paper Fill API reports 26.3 as the current Paper version.
• Spigot latest metadata reports build 4648 for the 26.3 line.
• Forge 26.3 remains covered by existing open PR feat: add Minecraft Forge 26.3 scroll #96; no duplicate Forge PR created.
• git diff --check passed; Mojang server URL is reachable.

[druid-infra]

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